The objective of this investigation is to study the role and alterations, if any, of the systemic and cardiac baroceptors in cardiovascular disease, specifically in experimental hypertension and myocardial infarction with hypotension and shock. Factors in the mechanism of resetting of the systemic and cardiac baroceptors in experimental hypertension will be analyzed by studying the function of the individual segments of the reflex loop. Reversal of the resetting after a period of normotension has been established will also be studied as to its occurrence, time factor, and mechanism. The role of cardiac vagal afferents in the hemodynamic alteration of acute myocardial infarction will be investigated in another study. It will be attempted to obtain experimental evidence for separation of the different cardiac reflex mechanisms as to their importance in the mechansism of altered hemodynamic regulation in experimental myocardial infarction with hypotension and shock.